The present invention relates to a superconductor and, more particularly, to an integrated superconductor suitable for use as, for example, a superconductive coil for a large scale, high intensity field magnet, generator and the like.
Large capacity current carrying superconductors with, for example, an available range of over 1000 amperes have been proposed wherein several monolithic superconductor members are provided, with each of the monolithic superconductor members including an extra fine multi-filamentary superconductor element fashioned of, for example, Nb-Ti or Nb.sub.3 Sn alloys, with the monolithic superconductor members being inserted into an appropriate slot or channel of a housing fashioned of a highly pure copper. A lid or cover member, also of highly pure copper is provided for covering an open end of the slot or channel so as to prevent the monolithic superconductor members from being displaced therefrom. Subsequent to the disposal of the monolithic superconductor members, an appropriate adhesive material such as, for example, solder is directed into the slot or channel so as to bind and integrate the lid or cover member along with the monolithic superconductor members into the housing.
A superconductor of the aforementioned type is generally disposed in a chamber and cooled by using a coolant such as, for example, liquid helium, with temperatures reaching below an extremely low temperature such as, for example, 4.2.degree. K., in order to maintain a superconductive state. In the event the superconductor is not maintained at predetermined low temperatures, the superconductive state, at least partially, changes into a normal conductive state and, in a large, high intensity field magnet, when the transition from a superconductive state to a normal conductive state affects the whole conductor, i.e., a quenching operation, a large amount of the stored energy burns out of the superconductive coil and an over-pressure results in a breakdown of a helium chamber. Consequently, a superconductor is usually constructed so that the heat generated during a partial normal conductive state is usually less than the heat capable of being cooled by the liquid helium.
In order to protect, e.g., superconductive coils from excessive temperatures during a superconductive-to-normal transition, it has been proposed to provide an external low resistance conductor across the superconductive coil terminals, with the relatively high pure copper housing and lid or cover member serving as an external low resistor so as to form a so-called "stabilizer" for the superconductor. Advantageously, the stabilizer is usually made of a highly pure copper.
Since a resistance value of pure aluminum is less than that of pure copper, it has been proposed to utilize aluminum in the fashioning of the stabilizer; however, when highly pure aluminum is used as a stabilizer and integrated by, for example, soldering or the like with the monolithic superconductive member covered with a high pure copper, it is extremely difficult to bond the pure aluminum to the monolithic superconductive member. Consequently, the high resistance at the bonding surfaces cause a considerable generation of heat such that no sufficient stable conductors may readily be obtained.
In, for example, Japanese Laid-Open Application No. 56-24361, it has been proposed to sandwich or interpose a monolithic superconductive member between stabilizers which are fashioned of pure aluminum bars covered with pipes of oxygen-free copper; however, a disadvantage of this proposal resides in the fact that the so constructed superconductor element has a soft weak aluminum portion and, consequently, is not suitable for use as a high intensity field magnet which requires the ability to endure strong magnetic forces.